Microsoft founder Bill Gates visited Nigeria this week, where he collaborated with Africa’s wealthiest man and the governors of several northern states on a new campaign to fight polio and other vaccine-preventable diseases.

The governors of four northern states gathered Wednesday in the city of Kaduna to sign memorandums of understanding with the Bill & Melinda Gates Foundation and the Dangote Foundation of Africa’s richest man, Aliko Dangote, along with the U.S. ambassador to Nigeria.

The MOUs kick-off programs that aim to raise childhood vaccination coverage to 80 percent by 2018. Gates Foundation country representative Mairo Mandara says Borno, Yobe, Sokoto and Kaduna states were chosen because they have the greatest need.

They join Kano and Bauchi states, which renewed their pre-existing agreements.

“If you look at the whole country, the lowest level of immunization are in these states where these MOUs are signed,” Mandara said.

He says vaccination rates are as low as 30 percent in some northern states.

Under the terms of the agreements, the Gates and Dangote foundations and the state governments will split the cost of initiatives like sending out teams to vaccinate children.

Polio

Another goal is to prevent polio from re-emerging. Nigeria has not reported a case of the disease since 2014. The World Health Organization said last year polio was no longer endemic in Nigeria.

But Mandara says there is still work to be done before the country can be declared polio-free.

“We need to maintain the immunity of children, the herd immunity so that when children travel to other areas they do not import the disease and bring it back,” he said.

Kaduna State Commissioner of Health and Human Services Andrew Jonathan Nok says he believes the new programs will help the state reach 100 percent vaccination coverage.

“So by the time we get this fully activated, which means we will even end up getting close to about 100 percent immunization in the respective local governments,” he said.

Mandara said she could not say yet how much would be spent on the new programs as the states’ needs are still being assessed.